media/audio/async_socket_io_handler.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_
   6 #define MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_
   7
   8 #include "base/message_loop/message_loop.h"
   9 #include "base/sync_socket.h"
  10 #include "base/threading/non_thread_safe.h"
  11 #include "media/base/media_export.h"
  12
  13 namespace media {
  14
  15 // The message loop callback interface is different based on platforms.
  16 #if defined(OS_WIN)
  17 typedef base::MessageLoopForIO::IOHandler MessageLoopIOHandler;
  18 #elif defined(OS_POSIX)
  19 typedef base::MessageLoopForIO::Watcher MessageLoopIOHandler;
  20 #endif
  21
  22 // Extends the CancelableSyncSocket class to allow reading from a socket
  23 // asynchronously on a TYPE_IO message loop thread.  This makes it easy to share
  24 // a thread that uses a message loop (e.g. for IPC and other things) and not
  25 // require a separate thread to read from the socket.
  26 //
  27 // Example usage (also see the unit tests):
  28 //
  29 // class SocketReader {
  30 //  public:
  31 //   SocketReader(base::CancelableSyncSocket* socket)
  32 //       : socket_(socket), buffer_() {
  33 //     io_handler.Initialize(socket_->handle(),
  34 //                           base::Bind(&SocketReader::OnDataAvailable,
  35 //                                      base::Unretained(this));
  36 //   }
  37 //
  38 //   void AsyncRead() {
  39 //     CHECK(io_handler.Read(&buffer_[0], sizeof(buffer_)));
  40 //   }
  41 //
  42 //  private:
  43 //   void OnDataAvailable(int bytes_read) {
  44 //     if (ProcessData(&buffer_[0], bytes_read)) {
  45 //       // Issue another read.
  46 //       CHECK(io_handler.Read(&buffer_[0], sizeof(buffer_)));
  47 //     }
  48 //   }
  49 //
  50 //   media::AsyncSocketIoHandler io_handler;
  51 //   base::CancelableSyncSocket* socket_;
  52 //   char buffer_[kBufferSize];
  53 // };
  54 //
  55 class MEDIA_EXPORT AsyncSocketIoHandler
  56     : public NON_EXPORTED_BASE(base::NonThreadSafe),
  57       public NON_EXPORTED_BASE(MessageLoopIOHandler) {
  58  public:
  59   AsyncSocketIoHandler();
  60   virtual ~AsyncSocketIoHandler();
  61
  62   // Type definition for the callback. The parameter tells how many
  63   // bytes were read and is 0 if an error occurred.
  64   typedef base::Callback<void(int)> ReadCompleteCallback;
  65
  66   // Initializes the AsyncSocketIoHandler by hooking it up to the current
  67   // thread's message loop (must be TYPE_IO), to do async reads from the socket
  68   // on the current thread.  The |callback| will be invoked whenever a Read()
  69   // has completed.
  70   bool Initialize(base::SyncSocket::Handle socket,
  71                   const ReadCompleteCallback& callback);
  72
  73   // Attempts to read from the socket.  The return value will be |false|
  74   // if an error occurred and |true| if data was read or a pending read
  75   // was issued.  Regardless of async or sync operation, the
  76   // ReadCompleteCallback (see above) will be called when data is available.
  77   bool Read(char* buffer, int buffer_len);
  78
  79  private:
  80 #if defined(OS_WIN)
  81   // Implementation of IOHandler on Windows.
  82   virtual void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
  83                              DWORD bytes_transfered,
  84                              DWORD error) OVERRIDE;
  85 #elif defined(OS_POSIX)
  86   // Implementation of base::MessageLoopForIO::Watcher.
  87   virtual void OnFileCanWriteWithoutBlocking(int socket) OVERRIDE {}
  88   virtual void OnFileCanReadWithoutBlocking(int socket) OVERRIDE;
  89
  90   void EnsureWatchingSocket();
  91 #endif
  92
  93   base::SyncSocket::Handle socket_;
  94 #if defined(OS_WIN)
  95   base::MessageLoopForIO::IOContext* context_;
  96   bool is_pending_;
  97 #elif defined(OS_POSIX)
  98   base::MessageLoopForIO::FileDescriptorWatcher socket_watcher_;
  99   // |pending_buffer_| and |pending_buffer_len_| are valid only between
 100   // Read() and OnFileCanReadWithoutBlocking().
 101   char* pending_buffer_;
 102   int pending_buffer_len_;
 103   // |true| iff the message loop is watching the socket for IO events.
 104   bool is_watching_;
 105 #endif
 106   ReadCompleteCallback read_complete_;
 107
 108   DISALLOW_COPY_AND_ASSIGN(AsyncSocketIoHandler);
 109 };
 110
 111 }  // namespace media.
 112
 113 #endif  // MEDIA_AUDIO_ASYNC_SOCKET_IO_HANDLER_H_